Replacing 3.55 with 4.09

Hey guys, I currently have 3.55 gears and due to running a taller tire on the street would like to swap to 4.09 gears. Can I use the frpp 4.09 ring and pinon kit with my differential? I'm having a hard time figuring it out based on the item description. Is there anything else I need to buy?

Yes you can run the 4.09 in that diff. Also yes you do need additional parts. Here is the kit:

https://www.americanmuscle.com/ford-performance-ring-and-pinionstallation-kit-1517.html

why not just 3.73 ..?

w3rkn said:

why not just 3.73 ..?

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Go big or go home. Actually I can do the 3.73s for just $200 in labor since I can easily work out a trade.

I just feel like if I'm spending $200 maybe I should just go all the way.

Well it must be a 30" tire or something crazy....if not you will hate 1st gear with the 4.09s

315 35 20 .... 28.7 diameter

H1shawn1 said:

315 35 20 .... 28.7 diameter

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I am running the same size tire on my Ecoboost. (don't ask...). I saw the other day american muscle has a 4.11 rear end gear which got me curious about rear ends larger than 3.73 in general. I've had a hard time finding any info or recent stories from people going larger than the 3.73. Keep us updated if you do it, I think it'll be cool and a good piece of information.

just seems so short. ive seen so many people going the opposite direction dropping gear, especially after boost.

This is just my perspective, I had a T-45 with 4.30 gears in my old GT and loved first gear not hated it and that's with ~1500 less rpm.

4.09 is only 8% larger than 3.73.

I would love to get ahold of a 2018 manual with a set of 4.56 gears. The thought of it puts a smile on my face.

3.73 with your taller tire will still be just a smidge shorter overall ratio than 3.55 with a stock tire.

I like your style. I ran 4.10s on my 2001 GT 5spd and loved every minute of it...especially 6k rpm clutch dumps on slicks. With the current S550 transmissions you won’t even have to fret highway excessive revs.

I had 4.09 in a 17 gt with 6r80 trans. With a vmp tune and gt350 Cai , 4 c converter ran consistent 12.30 at 112.8.
60 ft was 1.750.
No headers or intake manifold.
Car was fun as hell to drive. The Ford power packs tune can be set for the 4.09. Your looking at 2500 rpm at 70 mph in sixth gear.
I still have this diff an it will be going in my 18 pp manual soon.

People are scared of gear.

I want to stall mine and do at least 3.73s in my car with the Cobra Jet intake and on E85!

Whats next..5:13's? or not available for irs..